GH-Related Fluid Retention and Carpal Tunnel Syndrome

Growth hormone expands extracellular fluid volume by promoting renal sodium reabsorption, attributed largely to the epithelial sodium channel in the distal nephron together with activation of the renin-angiotensin-aldosterone system. The result is a genuine increase in total body water rather than a redistribution. It presents as peripheral oedema, puffiness of the hands and face, joint pain and stiffness, and carpal tunnel syndrome, the last of which is straightforwardly mechanical: swelling within an inelastic fibro-osseous tunnel compresses the median nerve.

These are the most common adverse effects of growth hormone in adults and they are clearly dose-related. In the trials of growth hormone in healthy older adults pooled by the 2007 Annals of Internal Medicine review, oedema, arthralgia and carpal tunnel syndrome occurred far more often on treatment than on placebo. The same signal reshaped practice in adult deficiency during the 1990s, when weight-based regimens carried over from paediatrics were abandoned for low starting doses titrated slowly against IGF-1.

Because they emerge early and track dose, these symptoms function as a practical ceiling signal, often appearing before IGF-1 has moved far out of range. They resolve on dose reduction, and their chronic counterpart is the soft-tissue overgrowth of acromegaly. Risk is higher in older people, at greater body weight, and in women taking oral oestrogen.

The misreading is cosmetic and common. Rapid weight gain over days, increased limb girth and a fuller looking musculature are read as anabolism when the timescale rules that out; fluid can accumulate in a week, contractile protein cannot. The same confusion runs in reverse when the water is lost on stopping and described as muscle loss. Carpal tunnel symptoms are also routinely attributed to training rather than to the dose that produced them.